This invention relates generally to movable barrier operators and more particularly to obstacle detection.
Movable barrier operators are known in the art. Such operators, including garage door operators, are often provided with a mechanism to detect when an obstacle lies in the path of the movable barrier. Upon sensing such an obstacle, movement of the movable barrier can be altered to avoid damage or injury to the obstacle and/or the movable barrier.
In some systems, a force limit (or force sensitivity) can be manually set. When this value is exceeded during movement of the movable barrier, as will typically occur when the movable barrier contacts an obstacle, an appropriate response can be effected. For example, the direction of travel of the movable barrier can be reversed to move the movable barrier away from the obstacle. In other systems, the speed of door travel is monitored. If the speed slows or stops, the operator determines that the movable barrier has contacted an obstacle and again the movable barrier can be stopped or its movement reversed.
One problem with such systems derives from the fact that the amount of force required to move a movable barrier over its entire travel limit may vary from place to place. Variations can also exist in a given place between closing and opening the movable barrier. In addition, mechanical noise due to sticking of the movable barrier can also contribute detectable artifacts that can simulate rapid force changes that can in turn cause an unwanted operator response.
Some prior art systems seek to remedy such problems by adjusting force sensitivity to make the operator less sensitive to such conditions. Unfortunately, reducing sensitivity in this way will also often make the operator less sensitive to detecting a genuine obstacle impact.
Other systems use so-called force profiling. Historical force information is stored in a force table and possibly updated from time to time to account for changes over time. Unfortunately, these systems, too, are sometimes subject to false triggering due at least in part to measurement anomalies during the operation of the movable barrier.